NCPTT

Replacing Trees in Historic Landscapes

This video was produced by NCPTT, in cooperation with the Olmsted Center for Landscape Preservation, and the Cane River Creole National Historical Park, all units of the National Park Service.

Hi, I am Charlie Pepper, at the Magnolia Plantation in Natchitoches, Louisiana.

This video provides guidance on the concepts and techniques of replacing individual trees at historic properties.

Trees in historic landscapes are often important cultural resources that contribute to the significance and integrity of a property. Preserving important trees in historic landscapes can present difficult and complex challenges.

Many of the inherent characteristics of trees, such as growth and the associated change in size, can seem incompatible with traditional preservation objectives of sustaining the original form of historic features. However, the fact that trees grow, age, and change in character does not diminish the fact that they are often important parts of the historic record that should be preserved.

Tree removal should be performed by a certified arborist

Even with the best of care, trees in historic landscapes will eventually deteriorate.

Common reasons for tree removal include:

• structural instability, which can pose serious safety hazards;
• adverse impacts to adjacent resources, such as tree roots damaging the foundation of a historic structure; or,
• an irreversible decline in health due to age, disease or pest infestation.

Removing an existing tree can be hazardous.  It should only be accomplished by a certified arborist.

Document existing conditions

When preparing to replace a tree at a historic property there are several steps that should be considered.  These include:

• documenting existing conditions,
• selecting the replacement tree, and
• using appropriate field techniques to minimize site disturbance.

Documenting information about the removal and replacement of trees in historic landscapes provides valuable information for future reference.  Prior to removing a deteriorated tree or planting a new one, record information about the condition of the existing tree and the site where it is growing.   These records are valuable for tracking preservation treatments and trends in resource condition over time.  They will be especially important when replanting is needed again in the future.

There may be fragile resources that will limit equipment access.

When selecting a replacement, it is important to retain the qualities of the original tree.  If possible, an in-kind replacement, propagated from the existing tree, should be used. Alternatively, a tree of the same species or one with similar qualities such as size, canopy shape, and foliage character, can be an acceptable substitute.

Several considerations before determining an appropriate replanting method include:

• Are recommendations from cultural resource specialists such as archeologists or landscape architects needed?
• And are there fragile resources (above and below ground) near the planting site that will limit equipment access?

Tree planting diagram

Standard horticultural tree planting methods involve using heavy equipment to prepare a hole that is 5 times the width of the rootball. This approach, while good for the tree, can cause major disturbance and significant damage to the site.  In resource sensitive areas with rich archeological features such as the slave quarters at Magnolia Plantation, standard horticultural planting methods can be modified to reduce damage to cultural resources.

We are going to be demonstrating two methods that minimize potential damage to historic features.

Mound Planting

Mound Planting

The first demonstration will be Mound Planting - a technique that is effective for replacing trees in locations where it is necessary to minimize ground disturbance.

This method mounds soil around a rootball that is placed in a slight depression in the existing grade and does not require digging a deep planting hole.

The mounding of soil can alter site grading and change the visual character of the landscape.  Because of this, it is best to use small replacement trees that will require minimal mounding to cover the rootball.

1. Using a pointed shovel or garden rake, remove the existing soil and vegetation to a depth of 2 or 3 inches in a circular area that is 5 times the diameter of the roots.
2. Remove all nursery packing material from the plant and accumulated material from the top of the rootball. In addition, using a knife or razor, vertically score the roots to encourage lateral growth.  Place the tree so the rootball rests solidly on the ground and the trunk is upright.
   

   Using a knife or razor, vertically score the roots to encourage lateral growth.

3. Mound around the tree using soil from the original location or fill that matches the original soil as closely as possible.
4. Taper the mounded soil into the surrounding grade and apply 1 or 2 inches of organic mulch, such as wood chips or pine straw, to prevent erosion.
5. Water well. Because the planting is above grade, the soil will be prone to drying.
6. Regularly monitor soil moisture and irrigate as needed.

Once the tree becomes established, which will take about one or two years, roots will extend beyond the mound and will be less susceptible to drying.

Planting Into a Decayed Stump

Planting into a decayed stump.

The next method is planting into a decayed stump. As with the mound planting, using a small replacement tree will require less digging and reduce the potential impact to adjacent cultural resources. This method is ideal for replacing trees in the exact location of the original to preserve the historically authentic character of the site.

1. Start by assessing the extent of decay in an existing stump.  Replanting within a stump will only be successful if decomposition is well advanced.  Ideally the stump should have minimal or no solid wood remaining.
2. The rootball needs to be small enough to easily fit into the decomposed area of the stump with at least 6 to 8 inches of additional space on each side for backfilling with soil.Using hand tools such as a pointed shovel and axe, break up and remove the decayed wood remaining within the stump.  Create adequate space for planting and backfilling with soil.
3. Once it has been properly prepared, elevate the top of the rootball 3 to 4 inches above the surrounding grade.  As the remaining stump decomposes over the next few years, the rootball will settle further into the hole.
4. Backfill the hole with soil that matches the original material as closely as possible.
5. Water the tree well to ensure good initial establishment.

Maintenance of a newly planted tree is critical to ensure its survival.

Apply 1 or 2 inches of organic mulch, such as wood chips or pine straw, to prevent erosion.

• Each week, for the first year after planting, apply approximately 1” of water through irrigation and/or rainfall.
• Do not fertilize unless there is a visible nutrient deficiency, such as yellowing of the foliage which can be confirmed by soil or tissue analysis.
• To encourage successful establishment, it is best to allow newly planted trees to sway gently in the wind.
• Staking should not be used unless the site is typically very windy and there is a chance that the rootball may uproot or become loose in the planting hole.

Long term success of the replacement tree can be enhanced by establishing and implementing a consistent preservation maintenance program that minimizes abrupt changes in tree care or to the landscape around it.

While all trees will eventually deteriorate and need to be removed, using replacement strategies covered in this video, will foster the preservation of landscapes and associated cultural resources at historic properties.

We hope this video has been helpful in explaining the concepts and techniques for replacing trees in historic landscapes.  If you would like additional information please see the National Park Service publication “Clippings” (pdf, 2.5MB) available online.

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